CN116583567A - color changeable adhesive sheet - Google Patents

Abstract

The adhesive sheet (S) which is the color-changing adhesive sheet of the present invention has an adhesive layer (10). The adhesive layer (10) contains: a polymer component having a microphase-separated structure including a first phase and a second phase, and a colorant capable of developing color by external stimulation. The colorant is compatible with the first phase and incompatible with the second phase.

Description

color changeable adhesive sheet

technical field

The invention relates to a color-changeable adhesive sheet.

Background technique

A display panel such as an organic EL panel has a laminated structure including a pixel panel, a protective member, and the like. In the manufacturing process of such a display panel, for example, a transparent adhesive sheet can be used to bond elements included in a laminated structure.

In addition, as a transparent adhesive sheet arranged on the light emitting side (image display side) of the pixel panel in the display panel, it has been proposed to use a preformed adhesive sheet for imparting design, light barrier properties, and lightening properties to predetermined parts of the adhesive sheet. Adhesive sheets for colored parts such as reflective materials. Such a pressure-sensitive adhesive sheet is described in, for example, Patent Document 1 below. Patent Document 1 specifically describes a PSA sheet having a colored portion containing a carbon black pigment.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2017-203810

Contents of the invention

The problem to be solved by the invention

However, in the case of using a pressure-sensitive adhesive sheet on which a colored portion is formed in advance in the manufacturing process of a display panel, after the pressure-sensitive adhesive sheet is attached to an adherend, it is not possible to properly inspect the difference between the adherend and the adherend. Check whether there are foreign objects and air bubbles between the colored parts of the combined sheet. For the bonding of an adhesive sheet in the display panel manufacturing process, it is required to be able to properly inspect whether there are foreign substances and air bubbles between the adherend and the adhesive sheet after the bonding.

On the other hand, from a viewpoint of securing the function of the colored part provided in the transparent adhesive sheet for display panels, it is required to suppress the deterioration of a colored part.

The present invention provides a color-changing pressure-sensitive adhesive sheet capable of discoloring at least a part of a pressure-sensitive adhesive layer after being attached to an adherend, and suitable for suppressing deterioration of the discolored portion of the pressure-sensitive adhesive layer.

means of solving problems

The present invention [1] includes a color-changing adhesive sheet having a color-changing adhesive layer, wherein the adhesive layer comprises: a color-changing adhesive sheet comprising a first phase and a second phase A polymer component of a microphase-separated structure, and a colorant capable of developing color by an external stimulus, the colorant having compatibility with the first phase and incompatibility with the second phase.

The present invention [2] includes the color-changing adhesive sheet described in the above [1], wherein the polymer component includes a polymer having a first segment and a second segment in the molecule, and the first segment The first phase is formed and the second segment forms the second phase.

The present invention [3] includes the color-variable adhesive sheet according to the above [2], wherein the polymer is a block polymer having a first polymer as the first segment block and a second polymer block as said second segment.

The present invention [4] includes the color-changing adhesive sheet described in the above [2], wherein the polymer is a graft polymer having a polymer main chain as the first segment and polymer side chains as said second segment.

The present invention [5] includes the color-variable adhesive sheet according to any one of the above-mentioned [1 to 4], wherein the mass ratio of the second phase in the polymer component is larger than that of the first phase Proportion.

The present invention [6] includes the color-changing adhesive sheet according to any one of the above-mentioned [1] to [5], wherein the colorant is a compound that develops color by reaction with an acid, and the adhesive The layer also contains a photoacid generator.

The present invention [7] includes the color-changing adhesive sheet described in the above [6], wherein the photoacid generator is compatible with the first phase and incompatible with the second phase. sex.

The present invention [8] includes the color-changing adhesive sheet described in any one of the above-mentioned [1] to [7], wherein the adhesive layer is formed by applying the external stimulus in a linear form to the adhesive layer. The first discoloration width W1 of the discoloration region formed in the agent layer, and the second discoloration width W2 of the discoloration region after further heat-treating the adhesive layer at 85°C for 120 hours satisfy 0.5≤W2/W1≤ 2.

The present invention [9] includes the color-changing adhesive sheet described in any one of the above-mentioned [1] to [8], wherein the adhesive layer is formed by applying the external stimulus in a linear form to the adhesive layer. The first discoloration width W1 of the discoloration region formed in the adhesive layer, and the third discoloration width W3 of the discoloration region after further heat-treating the adhesive layer at 65°C and a relative humidity of 90% for 120 hours satisfy 0.5 ≤W3/W1≤2.3.

Invention effect

In the color-variable adhesive sheet of the present invention, as described above, the adhesive layer contains a colorant capable of developing color by external stimulation. Therefore, after attaching the color-changing pressure-sensitive adhesive sheet to the adherend, by applying an external stimulus to the portion of the pressure-sensitive adhesive layer to be discolored (at least a part of the pressure-sensitive adhesive layer), the portion can be partially discolored. In such a color-changing PSA sheet, the presence or absence of foreign substances and air bubbles between the PSA sheet and an adherend can be inspected after lamination and before the discolored portion of the PSA layer is formed.

In addition, in the color-variable adhesive sheet, as described above, the adhesive layer contains a polymer component having a microphase-separated structure including a first phase and a second phase, and the colorant has a phase phase to the first phase. Compatibility, and not compatible with the second phase. Such a color-variable adhesive sheet is suitable for suppressing migration (diffusion, etc.) of the developed colorant after the adhesive layer forms a discolored portion (ie, after the colorant is developed by external stimulation). By suppressing the migration of the developed colorant, deterioration (bleeding, fading, color unevenness, etc.) of the discolored portion is suppressed.

Description of drawings

Fig. 1 is a schematic cross-sectional view of an embodiment of the color-changing adhesive sheet of the present invention.

FIG. 2 is a schematic diagram of an example of a microphase-separated structure in an adhesive layer. Figures 2A and 2B show spherical structures, Figures 2C and 2D show cylindrical structures, Figures 2E and 2F show helical structures, and Figure 2G shows layered structures.

3 is a schematic cross-sectional view of a modified example of the color-changing adhesive sheet of the present invention (the case where the color-changing adhesive sheet is a single-sided adhesive sheet with a substrate).

Fig. 4 shows an example of a method of using the color-variable pressure-sensitive adhesive sheet of the present invention. FIG. 4A shows a step of preparing a color-changing adhesive sheet and a member (adhered body), and FIG. 4B shows a step of bonding members to each other via a color-changing adhesive sheet. Fig. 4C shows a step of forming a discolored portion on an adhesive layer of a discolored adhesive sheet.

FIG. 5 is a TEM image of the adhesive layer of Example 1. FIG.

FIG. 6 is a TEM image of the adhesive layer of Example 2. FIG.

FIG. 7 is a TEM image of an adhesive layer of Comparative Example 1. FIG.

Detailed ways

As shown in FIG. 1 , an adhesive sheet S which is one embodiment of the color-changing adhesive sheet of the present invention has an adhesive layer 10 . The pressure-sensitive adhesive sheet S has a sheet shape with a predetermined thickness, and extends in a direction (surface direction) perpendicular to the thickness direction. The adhesive sheet S can be used, for example, as a transparent adhesive sheet arranged on the image display side of a pixel panel in a display panel (having a laminated structure including a pixel panel, a protective member, etc.) such as an organic EL panel.

The adhesive layer 10 is a pressure-sensitive adhesive layer formed from an adhesive composition. The pressure-sensitive adhesive layer 10 has transparency (visible light transmittance). The pressure-sensitive adhesive layer 10 includes a polymer component and a colorant capable of developing color by external stimulation described later. Such a portion of the pressure-sensitive adhesive layer 10 that receives an external stimulus can change color. That is, the transparency of the portion of the pressure-sensitive adhesive layer 10 that is subjected to external stimulation may decrease afterwards.

The polymer component is an adhesive component that exhibits adhesiveness in the adhesive layer 10 . The polymer composition exhibits rubber elasticity in the room temperature region. Examples of polymer components include acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, polysiloxane polymers, polyamide polymers, and fluoropolymers. thing. From the viewpoint of ensuring good transparency and adhesiveness in the pressure-sensitive adhesive layer 10 , it is preferable to use an acrylic polymer as the polymer component.

The polymer component has a microphase-separated structure including a first phase and a second phase in the adhesive layer 10 . The first phase is a phase compatible with the colorant. The second phase is a phase incompatible with the colorant. As the microphase separation structure, for example, a spherical structure (sea-island structure) as shown in Fig. 2A and Fig. 2B, a cylindrical structure as shown in Fig. 2C and Fig. 2D, a helical structure as shown in Fig. 2E and Fig. 2F like structure (double continuous phase structure), and layered structure as shown in Figure 2G.

In the structure shown in FIG. 2A , the first phase M1 is a spherical dispersed phase, and the second phase M2 is a matrix. In the structure shown in FIG. 2B , the first phase M1 is a matrix, and the second phase M2 is a spherical dispersed phase. In the structure shown in FIG. 2C , the first phase M1 is a cylindrical dispersed phase, and the second phase M2 is a matrix. In the structure shown in FIG. 2D , the first phase M1 is a matrix, and the second phase M2 is a columnar dispersed phase. In the structure shown in FIG. 2E , the first phase M1 has a three-dimensional network structure, and the second phase M2 is a matrix. In the structure shown in FIG. 2F , the first phase M1 is a matrix, and the second phase M2 has a three-dimensional network structure. In the structure shown in FIG. 2G , the plate-shaped first phase M1 and the plate-shaped second phase M2 repeat alternately. From the viewpoint of suppressing migration of the colorant in the adhesive layer 10, the polymer component has a microphase-separated structure as shown in FIG. 2A, FIG. 2C, or FIG. 2E.

The polymer component contains a polymer (first polymer) having a first segment forming a first phase and a second segment forming a second phase in a molecule. Examples of the first polymer include block polymers having a first polymer block as a first segment and a second polymer block as a second segment. A block polymer can have multiple blocks of a first polymer with different monomer compositions, or it can have multiple blocks of a second polymer with different monomer compositions (in this case, the block polymer is A multi-block copolymer in which the number of block types in the composition is 3 or more). Examples of the first polymer include graft polymers having a polymer main chain as a second segment and polymer side chains as a first segment. The graft polymer may have multiple polymer side chains with different monomer compositions, or may have multiple polymer blocks with different monomer compositions within the polymer main chain. The polymer component may contain one type of first polymer, or may contain multiple types of first polymers. In addition, the polymer component may contain a polymer (second polymer) other than the first polymer. The polymer component may contain one type of second polymer, or may contain multiple types of second polymers.

The first segment is a segment containing 80% by mass or more of the same monomer composition as the monomer solution judged to be compatible with the colorant by the compatibility judgment test described later in the examples (the monomer is selected from, for example, monomers listed below). The colorant is compatible with the first phase formed by such first segments. In the case where the colorant is hydrophilic, the first segment is preferably hydrophilic. In the case where the colorant is hydrophilic, the first segment is preferably a hard segment. The glass transition temperature of the hard segment is preferably 0°C or higher, more preferably 30°C or higher, and still more preferably 50°C or higher. In the case where the colorant is hydrophobic, the first segment is preferably hydrophobic. In the case where the colorant is hydrophobic, the first segment is preferably a soft segment. The glass transition temperature of the soft segment is preferably 0°C or lower, more preferably lower than 0°C, even more preferably -30°C or lower, particularly preferably -50°C or lower.

The second segment is a segment containing 80% by mass or more of the same monomer composition as that of the monomer solution judged to be incompatible with the colorant by the compatibility determination test described later in the Examples (monomers such as monomers listed below). The colorant has no compatibility with the second phase formed by such second segment. In the case where the colorant is hydrophilic, the second segment is preferably hydrophobic. In the case where the colorant is hydrophilic, the second segment is preferably a soft segment. The glass transition temperature of the soft segment is preferably 0°C or lower, more preferably lower than 0°C, even more preferably -30°C or lower, particularly preferably -50°C or lower. When the second segment is a soft segment, from the viewpoint of ensuring the adhesive force of the adhesive layer 10, the mass ratio of the second segment (second phase) in the polymer component is preferably larger than that of the first chain segment. The mass ratio of the segment (first phase). In the case where the colorant is hydrophobic, the second segment is preferably hydrophilic. When the colorant is hydrophobic, the second segment is preferably a hard segment. The glass transition temperature of the hard segment is preferably 0°C or higher, more preferably 30°C or higher, and still more preferably 50°C or higher.

Regarding the glass transition temperature (Tg) of the polymer (including a segment), a glass transition temperature (theoretical value) obtained from the following Fox formula can be used. The Fox formula is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of a monomer constituting the polymer. In the following Fox formula, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of the monomer i constituting the polymer, and Tgi represents the glass transition temperature of the homopolymer formed from the monomer i (℃). Regarding the glass transition temperature of homopolymers, literature values can be used, for example, in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Introduction to Synthetic Resins for Coatings" "( Kitaoka Kyo San, Polymer Press, 1995) the glass transition temperature of various homopolymers. On the other hand, the glass transition temperature of a homopolymer of a monomer can be obtained by the method specifically described in JP-A-2007-51271.

Fox formula: 1/(273+Tg)=Σ[Wi/(273+Tgi)]

When an acrylic polymer is used as the polymer component, the acrylic polymer is, for example, a copolymer of a monomer component containing an alkyl (meth)acrylate in a ratio of 50% by mass or more. "(Meth)acrylic" means acrylic and/or methacrylic.

As an alkyl (meth)acrylate, the alkyl (meth)acrylate which has a linear or branched C1-C20 alkyl group is mentioned, for example. Examples of such alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, ( Isopropyl methacrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, isopentyl (meth)acrylate ester, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, (meth) ) isooctyl acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate , dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, (meth) ) pentadecyl acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate nonadecyl (meth)acrylate and eicosyl (meth)acrylate. Alkyl (meth)acrylates may be used alone or in combination of two or more. As the alkyl (meth)acrylate forming the hard segment, it is preferable to use an alkyl acrylate having an alkyl group having 1 to 5 carbon atoms, and it is more preferable to use an alkyl acrylate selected from methyl acrylate, methyl methacrylate, and n-acrylate. At least one of the group consisting of butyl esters. As the alkyl (meth)acrylate forming the soft segment, it is preferable to use an alkyl acrylate having an alkyl group having 7 to 20 carbon atoms, and it is more preferable to use an alkyl acrylate selected from the group consisting of 2-ethylhexyl acrylate and dodecyl acrylate. At least one of the group consisting of base ester and stearyl acrylate.

From the viewpoint of appropriately expressing basic properties such as adhesiveness in the adhesive layer 10, the ratio of the alkyl (meth)acrylate in the monomer component is preferably 50% by mass or more, and more preferably 60% by mass or more. , and more preferably 70% by mass or more. This ratio is, for example, 99% by mass or less.

The monomer component may contain a copolymerizable monomer capable of copolymerizing with an alkyl (meth)acrylate. As a copolymerizable monomer, the monomer which has a polar group is mentioned, for example. Examples of the polar group-containing monomer include hydroxyl group-containing monomers, nitrogen atom-containing ring monomers, and carboxyl group-containing monomers. Polar group-containing monomers contribute to the modification of acrylic polymers, such as introducing crosslinking points to acrylic polymers and ensuring cohesion of acrylic polymers. In order to modify the acrylic polymer, the polar group-containing monomer may be contained in the hard segment or the soft segment.

The copolymerizable monomer preferably contains at least one selected from the group consisting of a hydroxyl group-containing monomer, a nitrogen atom-containing ring-containing monomer, and a carboxyl group-containing monomer. The copolymerizable monomer more preferably contains a hydroxyl group-containing monomer and/or a monomer having a nitrogen atom ring.

Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxy (meth)acrylate - Hydroxypropyl, 4-Hydroxybutyl (meth)acrylate, 6-Hydroxyhexyl (meth)acrylate, 8-Hydroxyoctyl (meth)acrylate, 10-Hydroxydecyl (meth)acrylate, ( 12-Hydroxylauryl meth)acrylate and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As the hydroxyl group-containing monomer, 4-hydroxybutyl (meth)acrylate is preferably used, and 2-hydroxybutyl acrylate is more preferably used.

From the viewpoint of introducing a crosslinked structure into the acrylic polymer and securing the cohesive force in the adhesive layer 10, the proportion of the hydroxyl group-containing monomer in the monomer component is preferably 1% by mass or more, more preferably 3% by mass % or more, more preferably 5% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (relevant to the compatibility of various additive components in the adhesive layer 10 and the acrylic polymer), the ratio is preferably 30% by mass or less, and more preferably 20% by mass. Mass% or less.

Examples of monomers having a ring containing a nitrogen atom include: N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine , N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl Azole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3 -Morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-/> Oxin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinyliso/> Azole, N-vinylthiazole and N-vinylisothiazole. As the monomer having a ring containing a nitrogen atom, N-vinyl-2-pyrrolidone is preferably used.

From the viewpoint of ensuring the cohesion in the adhesive layer 10 and ensuring the adhesion to the adherend in the adhesive layer 10, the ratio of the monomer having a nitrogen atom ring in the monomer component is preferably 1 mass % or more, more preferably 3% by mass or more, even more preferably 5% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (relevant to the compatibility of various additive components in the adhesive layer 10 with the acrylic polymer), the ratio Preferably it is 30 mass % or less, More preferably, it is 20 mass % or less.

Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

From the viewpoint of introducing a crosslinked structure into the acrylic polymer, ensuring the cohesion in the adhesive layer 10, and ensuring the adhesion to the adherend in the adhesive layer 10, the carboxyl group-containing The proportion of the monomer is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid, the ratio is preferably 30% by mass or less, more preferably 20% by mass or less.

The monomer component may contain other copolymerizable monomers. Examples of other copolymerizable monomers include acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing Monomeric and aromatic vinyl compounds.

As an acid anhydride monomer, maleic anhydride and itaconic anhydride are mentioned, for example.

Examples of monomers containing sulfonic acid groups include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (methyl) ) acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate and (meth)acryloyloxynaphthalenesulfonic acid.

As a monomer containing a phosphoric acid group, 2-hydroxyethylacryloyl phosphate is mentioned, for example.

Examples of epoxy group-containing monomers include epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl (meth)acrylate, allyl glycidyl ether, etc. and glycidyl (meth)acrylate.

Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

Examples of the alkoxy group-containing monomer include alkoxyalkyl (meth)acrylates and alkoxyalkylene glycol (meth)acrylates. Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-methoxy (meth)acrylate, - ethoxyethyl, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate and ethoxypropyl (meth)acrylate. Examples of alkoxyalkylene glycol (meth)acrylates include methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (meth)acrylate. As the alkoxy group-containing monomer forming the hard segment, 2-methoxyethyl acrylate is preferably used.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene and vinyltoluene. Examples of olefins include ethylene, butadiene, isoprene and isobutylene. Styrene is preferably used as the aromatic vinyl compound forming the hard segment.

A copolymerizable monomer may be used individually or in combination of 2 or more types.

The polymer component preferably has a polymer selected from the group consisting of a polymer of methyl methacrylate (MMA), a copolymer of MMA and 4-hydroxybutyl acrylate (4HBA), a polymer of styrene, and a copolymer of styrene and 4HBA. At least one of them is used as a hard segment. The polymer component preferably has at least one selected from the group consisting of a polymer of 2-ethylhexyl acrylate (2EHA) and a copolymer of 2EHA and 4HBA as a soft segment.

The acrylic polymer can be formed by polymerizing the above-mentioned monomer components. As a polymerization method, for example, solution polymerization, bulk polymerization, and emulsion polymerization are mentioned, and solution polymerization is preferable. The acrylic block polymer can be synthesized, for example, by synthesizing the first segment by living polymerization such as RAFT polymerization in a solution, and then in a solution containing a monomer for forming the second segment and the first segment in the polymerization reaction. Alternatively, the acrylic block polymer can be synthesized by synthesizing the second segment by living polymerization such as RAFT polymerization in solution, and then adding the monomers used to form the first segment and the second segment Polymerization in solution. Acrylic graft polymers can be synthesized, for example, by combining a macromonomer (a polymer having a polymerizable double bond at one end) for forming a graft chain and a monomeric monomer for elongating the polymer backbone. Polymerization reaction in solution. Alternatively, the acrylic graft polymer can be synthesized, for example, by performing a polymerization reaction (graft polymerization) to elongate the polymer side chain after synthesizing the polymer main chain. As a polymerization initiator, for example, a thermal polymerization initiator is used. The usage-amount of a polymerization initiator is 0.05 mass part or more with respect to 100 mass parts of monomer components, and is 1 mass part or less, for example.

As a thermal polymerization initiator, an azo polymerization initiator and a peroxide polymerization initiator are mentioned, for example. Examples of the azo polymerization initiator include: 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2- Dimethyl methylpropionate, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride Salt, 2,2'-Azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-Azobis(2-methylpropionamidine ) disulfate and 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride. Examples of peroxide polymerization initiators include dibenzoyl peroxide, tert-butyl peroxymaleate, and lauroyl peroxide.

The weight average molecular weight of the acrylic polymer is preferably 100,000 or more, more preferably 300,000 or more, and still more preferably 500,000 or more, from the viewpoint of securing the cohesive force in the pressure-sensitive adhesive layer 10 . The weight average molecular weight is preferably 5,000,000 or less, more preferably 3,000,000 or less, still more preferably 2,000,000 or less. The weight-average molecular weight of the acrylic polymer was measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

The glass transition temperature (Tg) of the acrylic polymer is preferably 0°C or lower, more preferably -10°C or lower, even more preferably -20°C or lower. The glass transition temperature is, for example, -80°C or higher.

From the viewpoint of introducing a crosslinked structure into the polymer component, the adhesive composition may contain a crosslinking agent. As a crosslinking agent, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, Azoline crosslinkers, aziridine crosslinkers, carbodiimide crosslinkers and metal chelate crosslinkers. A crosslinking agent may be used individually or in combination of 2 or more types.

Examples of the isocyanate crosslinking agent include toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated Diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenylisocyanate. Moreover, derivatives of these isocyanates are also mentioned as an isocyanate crosslinking agent. Examples of the isocyanate derivative include modified isocyanurate and modified polyol. Examples of commercially available isocyanate crosslinking agents include: Coronate L (trimethylolpropane adduct of toluene diisocyanate, manufactured by Tosoh), Coronate HL (trimethylolpropane of hexamethylene diisocyanate) adduct, manufactured by Tosoh), Coronate HX (isocyanurate body of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals).

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, vinyl glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1 , 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N,N,N',N'-tetraglycidyl-isophenylene Methylamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

From the viewpoint of securing the cohesive force of the pressure-sensitive adhesive layer 10, the compounding amount of the crosslinking agent is, for example, 0.01 mass parts or more, preferably 0.05 mass parts or more, and more preferably 0.07 mass parts or more with respect to 100 mass parts of the polymer component. . From the viewpoint of ensuring good viscosity, the compounding amount of the crosslinking agent is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the polymer component.

In the case of introducing a crosslinked structure into a polymer component, a crosslinking catalyst may be used in order to efficiently advance the crosslinking reaction. As the crosslinking catalyst, for example, dibutyltin dilaurate, tetra-n-butyl titanate, tetraisopropyl titanate, iron triacetylacetonate (Na-Sem second iron) and butyltin oxide are preferably used. Dibutyltin laurate. The usage-amount of a crosslinking catalyst is 0.0001 mass part or more and 1 mass part or less with respect to 100 mass parts of polymer components, for example.

When a crosslinking catalyst is used, a crosslinking inhibitor that can be removed from the adhesive composition afterward may be added to the adhesive composition. When dibutyltin dilaurate is used as a crosslinking catalyst, acetylacetone is preferably used as a crosslinking inhibitor. In this case, in the adhesive composition, acetylacetone coordinates with dibutyltin dilaurate to suppress the crosslinking reaction of the crosslinking agent to the polymer component. In the production process of the pressure-sensitive adhesive sheet S described later, after the adhesive composition is coated on the release film to form a coating film, by heating at a desired point of time, acetylacetone can be volatilized and removed from the coating film. removed. Thereby, the crosslinking reaction of a crosslinking agent can progress.

The compounding quantity of a crosslinking inhibitor is 100 mass parts or more with respect to 100 mass parts of crosslinking catalysts, Preferably it is 1000 mass parts or more. In addition, this compounding quantity is 5000 mass parts or less, for example.

The colorant is compatible with the first phase and incompatible with the second phase. The colorant is preferably a compound that develops color by reaction with an acid (color-developing compound). When the colorant is a color-developing compound, the adhesive composition further contains a photoacid generator.

Examples of color-forming compounds include leuco dyes, triarylmethane dyes, diphenylmethane dyes, fluoran dyes, spiropyran dyes, and rhodamine dyes. The color-forming compounds may be used alone or in combination of two or more.

Examples of leuco dyes include 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H] xanthene], 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipropylamino-6-methyl-7-anilinofluoran, 3-diethylamino- 6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-dimethylanilinofluoran and 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide.

Examples of triarylmethane dyes include p,p',p"-tris-dimethylaminotriphenylmethane. Examples of diphenylmethane dyes include 4,4-bis-dimethylamino Phenyl benzhydryl benzyl ether. As a fluorane dye, for example: 3-diethylamino-6-methyl-7-chlorofluorane. As a spiropyran dye, for example: 3-methyl base spirobinaphthopyran. As a rhodamine dye, for example, rhodamine-B-anilinolactam can be mentioned.

From the viewpoint of ensuring good colorability in the adhesive layer 10, it is preferable to use a leuco pigment as the color-developing compound, and it is more preferable to use 2'-anilino-6'-(N-ethyl-N-iso Amylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthene].

The compounding amount of the color-forming compound is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, with respect to 100 parts by mass of the polymer component. The compounding amount is preferably 10 parts by mass or less, more preferably 7 parts by mass or less.

Photoacid generators generate acid by irradiating active energy rays as an external stimulus. Therefore, in the portion of the pressure-sensitive adhesive layer 10 irradiated with active energy rays, an acid is generated by the photoacid generator, and the color-developing compound is developed by the acid. From the viewpoint of favorable color development of the color-developing compound, the photoacid generator is preferably compatible with the first phase and incompatible with the second phase. The portion of the pressure-sensitive adhesive layer 10 irradiated with active energy rays is colored, for example, dark in color by the color development of the color-forming compound. The type of active energy ray is determined according to the type of photoacid generator (specifically, the wavelength of the active energy ray from which the photoacid generator generates acid). Examples of active energy rays include ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, and γ-rays. From the viewpoint of the variety of equipment used and ease of handling, ultraviolet rays are preferably used as active energy rays.

As a photoacid generator, an onium compound which generates an acid by ultraviolet irradiation is mentioned, for example. Onium compounds are provided, for example, in the form of onium salts of onium cations and anions. Examples of the onium cation include iodonium and sulfonium. Examples of anions include Cl ^- , Br ^- , I ^- , ZnCl ₃ ^- , HSO ₃ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ - , SbF ₆ ^{- ,} CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ HSO ₃ ^- , (C ₆ F ₅ ) ₄ B ^- and (C ₄ H ₉ ) ₄ B ^- . A photoacid generator may be used individually or in combination of 2 or more types. The adhesive composition preferably contains an onium salt (onium compound) containing sulfonium and C ₄ F ₉ HSO ₃ ^- as a photoacid generator.

The compounding amount of the acid generator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 5 parts by mass or more, particularly preferably 7 parts by mass or more, based on 100 parts by mass of the polymer component. The compounding amount is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

The compounding amount of the acid generator is, for example, 100 parts by mass or more, preferably 200 parts by mass or more, more preferably 300 parts by mass or more, and still more preferably 330 parts by mass or more, based on 100 parts by mass of the color-developing compound. The compounding amount is preferably not more than 1000 parts by mass, more preferably not more than 700 parts by mass, and still more preferably not more than 500 parts by mass.

The adhesive composition may contain other components as needed. Examples of other components include silane coupling agents, tackifiers, plasticizers, softeners, antioxidants, surfactants, and antistatic agents.

The pressure-sensitive adhesive sheet S can be manufactured by, for example, coating the above-mentioned adhesive composition on a release film (first release film) to form a coating film, and then drying the coating film (in FIG. The pressure-sensitive adhesive sheet S) is arranged on the release film L.

As a release film (release liner), a flexible plastic film is mentioned, for example. As this plastic film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film are mentioned, for example. The thickness of the release film is, for example, 3 μm or more, and, for example, 200 μm or less. The surface of the release film is preferably subjected to a release treatment.

Examples of coating methods for the adhesive composition include roll coating, lick roll coating, gravure coating, reverse coating, roll brush coating, spray coating, dip roll coating, bar coating, and doctor blade coating. Coating, air knife coating, curtain coating, lip die coating and die coating machines. The drying temperature of the coating film is, for example, 50°C to 200°C. The drying time is, for example, 5 seconds to 20 minutes.

When the adhesive composition contains a crosslinking agent, the crosslinking reaction proceeds by aging simultaneously with the above-mentioned drying or after drying. The aging conditions are appropriately set according to the type of crosslinking agent. The aging temperature is, for example, 20°C to 160°C. The aging time is, for example, 1 minute to 7 days.

Before or after aging, a release film (second release film) may be further laminated on the adhesive layer 10 on the first release film. The second release film is a flexible plastic film subjected to surface release treatment, and the same release film as above can be used for the first release film.

As described above, it is possible to manufacture a PSA sheet S in which the PSA surface is covered and protected with a release film. When using the adhesive sheet S, each release film is peeled from the adhesive sheet S as needed.

From the viewpoint of securing sufficient adhesiveness to an adherend, the thickness of the adhesive layer 10 is preferably 10 μm or more, more preferably 15 μm or more. From the viewpoint of the handleability of the adhesive sheet S, the thickness of the adhesive layer 10 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, particularly preferably 50 μm or less.

The haze of the adhesive layer 10 (haze before external stimulus is applied to the adhesive layer 10 ) is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. Such a configuration is suitable for checking the presence or absence of foreign matter and air bubbles between the PSA sheet S and the adherend after the PSA sheet S is bonded to the adherend. The haze of the pressure-sensitive adhesive layer 10 can be measured using a haze meter according to JIS K7136 (2000). As a haze meter, "NDH2000" by Nippon Denshoku Industries Co., Ltd., and "HM-150 type" by Murakami Color Technology Laboratory Co., Ltd. are mentioned, for example.

The average transmittance of the adhesive layer 10 in the wavelength range of 400 nm to 700 nm (the average transmittance before external stimulation is applied to the adhesive layer 10) is preferably 80% or more, more preferably 85% or more, and even more preferably 90%. %above. Such a configuration is suitable for checking the presence or absence of foreign matter and air bubbles between the PSA sheet S and the adherend after the PSA sheet S is bonded to the adherend.

After bonding to the glass plate, in the peeling test under the peeling conditions of 23°C, peeling angle 180° and peeling speed (stretch speed) 300mm/min, the adhesion of the adhesive sheet S to the stainless steel plate was shown. The resultant force is, for example, 1 N/25 mm or more, and, for example, 50 N/25 mm or less.

In the adhesive sheet S, the first discoloration width W1 of the discoloration region formed in the adhesive layer 10 by applying an external stimulus to the adhesive layer 10 in a linear form, and further, the adhesion at 85° C. The second discoloration width W2 of the discoloration region after the agent layer 10 is heat-treated for 120 hours satisfies the following formula (1).

0.5≤W2/W1≤2...(1)

Such a constitution is suitable for suppressing deterioration (bleeding, discoloration, color unevenness, etc.) of the discolored portion formed in the adhesive layer 10, and thus, contributes to maintaining the functional characteristics assumed by the discolored portion.

The first discoloration width W1 of the discoloration region formed in the adhesive layer 10 by applying external stimuli to the adhesive layer 10 in a linear shape, and the adhesive layer was further tested at 65° C. and a relative humidity of 90%. 10 The third discoloration width W3 of the discoloration region after heat treatment for 120 hours satisfies the following formula (2).

0.5≤W3/W1≤2.3...(2)

Such a constitution is suitable for suppressing deterioration (bleeding, discoloration, color unevenness, etc.) of the discolored portion formed in the adhesive layer 10, and thus, contributes to maintaining the functional characteristics assumed by the discolored portion.

As shown in FIG. 3 , the PSA sheet S may be a single-sided PSA sheet with a base material having a base material 20 in addition to the PSA layer 10 . In this case, specifically, the pressure-sensitive adhesive sheet S has the pressure-sensitive adhesive layer 10 and the substrate 20 arranged on one surface side in the thickness direction thereof. The substrate 20 is preferably in contact with one surface of the pressure-sensitive adhesive layer 10 in the thickness direction.

The substrate 20 is an element functioning as a transparent support. The base material 20 is, for example, a flexible plastic film. Examples of the constituent material of the plastic film include polyolefin, polyester, polyamide, polyimide, polyvinyl chloride, polyvinylidene chloride, cellulose, polystyrene, and polycarbonate. Examples of polyolefins include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/ Vinyl acetate copolymers, ethylene/ethyl acrylate copolymers, and ethylene/vinyl alcohol copolymers. Examples of polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Examples of polyamides include polyamide 6, polyamide 6,6, and partially aromatic polyamides. For the base material 20, the plastic material of the base material 20 is preferably polyester, more preferably polyethylene terephthalate, from the viewpoint of both transparency and mechanical strength.

The base material 20 has transparency. The haze of the substrate 20 is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less. The haze of the substrate 20 can be measured using a haze meter according to JIS K7136 (2000).

The surface of the substrate 20 on the side of the adhesive layer 10 may be subjected to physical treatment, chemical treatment, or primer treatment in order to improve adhesion to the adhesive layer 10 . Examples of physical treatment include corona treatment and plasma treatment. Examples of chemical treatment include acid treatment and alkali treatment.

From the viewpoint of ensuring the strength of substrate 20 functioning as a support, the thickness of substrate 20 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 20 μm or more. In addition, from the viewpoint of achieving moderate flexibility in the adhesive sheet S, the thickness of the substrate 20 is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

The pressure-sensitive adhesive sheet S shown in FIG. 3 can be manufactured by the method similar to the above-mentioned pressure-sensitive adhesive sheet manufacturing method except having used the base material 20 instead of a 1st release film, for example.

An example of the usage method of the adhesive sheet S is shown in FIG. 4A - FIG. 4C. This method includes a preparation step, a joining step, and a discoloration part forming step.

First, as shown in FIG. 4A , an adhesive sheet S, a first member 31 , and a second member 32 are prepared in a preparation step. The first member 31 is, for example, a display panel such as an organic EL panel. The first member 31 may be other electronic and optical devices. The second member 32 is, for example, a transparent substrate. Examples of the transparent substrate include transparent plastic substrates and transparent glass substrates.

Next, as shown in FIG. 4B , the first member 31 and the second member 32 are joined via the adhesive sheet S in a joining step. In this way, a laminated body Z was obtained. In the laminate Z, the PSA sheet S is arranged in contact with one surface of the first member 31 in the thickness direction, and the second member 32 is arranged in contact with one surface of the PSA sheet S in the thickness direction.

After the bonding process, the presence or absence of foreign matter and bubbles is checked between the members 31 and 32 and the adhesive sheet S as necessary.

Next, as shown in FIG. 4C , an external stimulus is applied to the adhesive layer 10 in the laminate Z in the discoloration portion forming process, thereby forming the discoloration portion 11 in the adhesive layer 10 . Specifically, the adhesive layer 10 is irradiated with active energy rays as external stimuli from the side of the transparent second member 32 through a mask pattern (not shown) for shielding a predetermined region of the adhesive layer 10 . As a result, discoloration occurs in the portion of the adhesive layer 10 that is not shielded by the mask pattern.

As a light source for active energy ray irradiation in this process, an ultraviolet LED lamp, a high pressure mercury lamp, and a metal halide lamp are mentioned, for example. In addition, in the active energy ray irradiation in this step, a wavelength cut filter for cutting the wavelength range of part of the active energy rays emitted from the light source may be used as needed.

In this step, in the portion of the adhesive layer 10 irradiated with active energy rays, an acid is generated by the photoacid generator, and the color-developing compound develops color by reaction with the acid. The discoloration portion 11 is thereby formed in the adhesive layer 10 .

For example, as described above, the pressure-sensitive adhesive sheet S can be used for bonding between members. When the first member 31 is a display panel such as an organic EL panel, by providing the discoloration portion 11 in a pattern shape corresponding to (that is, facing) the metal wiring formed on the pixel panel included in the panel, the metal wiring can be suppressed. of external light reflections.

As described above, the adhesive layer 10 in the adhesive sheet S contains a colorant capable of developing color by external stimulation. Therefore, after bonding the adhesive sheet S to the adherends (the members 31 and 32 in this embodiment), by applying an external stimulus to the portion to be discolored in the adhesive layer 10, it is possible to make the adhesive layer 10 Partial discoloration. The pressure-sensitive adhesive sheet S capable of forming the discolored portion 11 in the pressure-sensitive adhesive layer 10 after being attached to the adherend can be inspected after being attached and before the discolored portion 11 of the adhesive layer 10 is formed. Whether there are foreign objects and air bubbles between the stickies.

In addition, as described above, the pressure-sensitive adhesive layer 10 in the pressure-sensitive adhesive sheet S contains a polymer component having a microphase-separated structure including a first phase and a second phase, and the color-developing compound as a colorant is The first phase is compatible and not compatible with the second phase. In such an adhesive sheet S, after the color-forming compound is formed in the adhesive layer 10 (that is, after the color-developing compound is colored by external stimulation), the color-developing compound tends to stay in the region of the first phase, so it is suitable. It is used to suppress migration (diffusion, etc.) of the color-forming compound in the adhesive layer 10 . By suppressing the migration of the color-forming compound, deterioration (bleeding, fading, color unevenness, etc.) of the discolored portion is suppressed.

As described above, the pressure-sensitive adhesive sheet S can discolor at least a part of the pressure-sensitive adhesive layer 10 after bonding to an adherend, and is suitable for suppressing deterioration of the discolored portion of the pressure-sensitive adhesive layer 10 . Suppression of deterioration of the discolored portion in the adhesive layer 10 contributes to maintaining the functional characteristics of the discolored portion, such as designability, light barrier properties, and antireflection properties.

Example

Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to an Example. In addition, specific numerical values such as compounding amount (content), physical property values, and parameters described below may be replaced with the upper limits of the compounding amount (content), physical property values, parameters, etc. corresponding to them described in the above-mentioned "Detailed Embodiments" (a value defined as "below" or "less than") or a lower limit (a value defined as "above" or "greater than").

[Example 1]

<Preparation of polymer components>

In a reaction vessel with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, bis{4-[ 1.45 parts by mass of ethyl-(2-acetoxyethyl)carbamoyl]benzyl}trithiocarbonate, 0.12 parts by mass of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator A mixture of 36 parts by mass of anisole and 36 parts by mass of anisole as a solvent was stirred at 130° C. under a nitrogen atmosphere for 7 hours (polymerization reaction). Thus, a copolymer of styrene and 4HBA (styrene-4HBA copolymer) was obtained. The weight average molecular weight (Mw) of this copolymer was 26,000.

Next, in a reaction vessel with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 70 parts by mass of 2-ethylhexyl acrylate (2EHA), 30 parts by mass of the above-mentioned styrene-4HBA copolymer (solid content conversion amount), a mixture of 0.04 parts by mass of 2,2'-azobis(isobutyrate) dimethyl as a polymerization initiator and 57 parts by mass of ethyl acetate as a solvent was stirred at 75°C under a nitrogen atmosphere for 7 hours (polymerization). Thus, a polymer solution (polymer solution P ₁ ) containing an acrylic block polymer was obtained. The weight average molecular weight (Mw) of the acrylic block polymer in this polymer solution _P1 was 86,000. Additionally, the acrylic block polymer has a styrene-4HBA copolymer block (first polymer block) as the hard segment (first segment) and a 2EHA polymeric block as the soft segment (second segment) material block (second polymer block).

<Preparation of Adhesive Composition>

In the polymer solution _P1 containing an acrylic block polymer, an isocyanate crosslinking agent (trade name "Takenate D110N" , a 75% ethyl acetate solution of a trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals Co., Ltd.) 0.25 parts by mass (in terms of solid content), dibutyltin dilaurate ( Trade name "OL-1", 1% by mass ethyl acetate solution, manufactured by Tokyo Fine Chemicals Co., Ltd.) 0.01 parts by mass (solid content conversion amount), acetylacetone 3 as a crosslinking inhibitor (ligand for the crosslinking catalyst) Parts by mass, a colorless pigment (trade name "S-205", 2'-anilino-6'-(N-ethyl-N-isoamylamino)-3'-methylspiro [Phthalide-3,9'-[9H]xanthene], manufactured by Yamada Chemical Industry Co., Ltd.) 2 parts by mass, photoacid generator (trade name "SP-056", sulfonium and C ₄ F ₉ HSO ₃ ^- Onium salt of ADEKA Co., Ltd.) 7 parts by mass were mixed to prepare an adhesive composition.

<Formation of Adhesive Layer>

On the release-treated surface of a substrate film (trade name "MRF#38", polyester film, manufactured by Mitsubishi Plastics Co., Ltd.) with a thickness of 38 μm that has been subjected to release treatment on one side, an adhesive composition is applied to form a coating film . Next, this coating film was dried by heating at 132° C. for 3 minutes. Thereby, an adhesive layer with a thickness of 25 μm was formed on the base film. Then, on the adhesive layer on the base film, the release-treated surface of a release film with a thickness of 38 μm (trade name "MRE#38", polyester film, manufactured by Mitsubishi Plastics Co., Ltd.) subjected to release treatment on one side was attached. . Then, aging treatment was performed at 60° C. for 24 hours to advance the crosslinking reaction in the adhesive layer. As described above, the PSA sheet of Example 1 was produced. The composition of the polymer component and the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of Example 1 is shown in Table 1 in units of parts by mass (the same applies to Examples and Comparative Examples described later).

[Example 2]

In a reaction vessel with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet pipe, a macromer (commercial product) containing 75 parts by mass of 2-ethylhexyl acrylate (2EHA) and methyl methacrylate (MMA) was Name "AA-6", manufactured by Toagosei Co., Ltd.) 20 parts by mass, 4-hydroxybutyl acrylate (4HBA) 5 parts by mass, 2,2'-azobisisobutyronitrile (AIBN) 0.2 mass parts as a polymerization initiator parts, a mixture of 80 parts by mass of ethyl acetate as a solvent and 50 parts by mass of methyl ethyl ketone was stirred at 60° C. under a nitrogen atmosphere for 7 hours (polymerization reaction). Thus, a polymer solution (polymer solution P ₂ ) containing an acrylic graft polymer was obtained. The weight average molecular weight (Mw) of the acrylic graft polymer in this polymer solution _P2 was 350,000. In addition, the acrylic graft polymer has a polymer main chain as a soft segment (second segment) containing 2EHA as a main component; and as a hard segment (first segment) segment), the hard segment (first segment) contains MMA as a main component. Furthermore, the PSA sheet of Example 2 was produced in the same manner as the PSA sheet of Example 1 except that the polymer solution _P2 was used instead of the polymer solution _P1 in the preparation of the adhesive composition.

[Comparative example 1]

In a reaction vessel with a stirrer, a thermometer, a reflux condenser and a nitrogen gas introduction tube, 63 parts by mass of 2-ethylhexyl acrylate (2EHA), 9 parts by mass of methyl methacrylate (MMA), 2- 13 parts by mass of hydroxyethyl ester (HEA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 0.2 parts by mass as a solvent A mixture of 233 parts by mass of ethyl acetate was stirred at 60° C. under a nitrogen atmosphere for 7 hours (polymerization reaction). Thus, a polymer solution (polymer solution P ₃ ) containing an acrylic polymer was obtained. The weight average molecular weight (Mw) of the acrylic polymer in this polymer solution _P3 was 1.2 million. In addition, the acrylic polymer is a random copolymer. Furthermore, the PSA sheet of Comparative Example 1 was produced in the same manner as the PSA sheet of Example 1 except that the polymer solution _P3 was used instead of the polymer solution _P1 in the preparation of the PSA composition.

<Presence or absence of microphase separation structure>

About the PSA layer of each PSA sheet of Examples 1, 2 and Comparative Example 1, the presence or absence of a microphase separation structure was confirmed as follows. First, a sample for observation by a transmission electron microscope (TEM) is produced. Specifically, quick freezing was performed after the adhesive layer was dyed, and thin slices were cut out from the adhesive layer using an ultramicrotome (manufactured by Leica Corporation). Then, this thin section was observed and photographed using a transmission electron microscope (trade name "HT7820", manufactured by Hitachi High-Tech Co., Ltd.). Next, the obtained TEM images were analyzed and binarized by image analysis software.

As shown in FIG. 5 , in the PSA layer of the PSA sheet of Example 1, a microphase separation structure was confirmed. The microphase separation structure of the adhesive layer is a spherical structure as shown in FIG. 2A . Specifically, in the adhesive layer, benzene as a hard segment (first segment) is dispersed in a matrix (second phase) formed by a 2EHA block as a soft segment (second segment). A dispersed phase formed by ethylene-4HBA copolymer blocks.

As shown in FIG. 6 , a microphase separation structure was confirmed in the PSA layer of the PSA sheet of Example 2. The microphase separation structure of the adhesive layer is a spherical structure as shown in FIG. 2A . Specifically, in the adhesive layer, in a matrix (second phase) formed as a polymer main chain that is a soft segment (second segment) containing 2EHA and 4HBA as main components, MMA as the main component is dispersed. and 4HBA as the main component of the hard segment (first segment) of the polymer side chain to form a dispersed phase.

As shown in FIG. 7 , no microphase separation structure was confirmed in the pressure-sensitive adhesive layer of Comparative Example 1.

<Compatibility Judgment Test>

For each color-developing compound and photoacid generator used in Examples 1 and 2 and Comparative Example 1, compatibility with various monomers was examined.

Specifically, first, styrene, 4-hydroxybutyl acrylate (4HBA), methyl methacrylate (MMA), acrylic acid, N-vinyl-2-pyrrolidone (NVP), 2-methoxyethyl acrylate Each solution of ester (2MEA), methyl acrylate, 2-ethylhexyl acrylate (2EHA), lauryl acrylate (lauryl acrylate) and stearyl acrylate (octadecyl acrylate) solution. A mixed solution of 95% by mass of styrene and 5% by mass of 4HBA was also prepared as a monomer solution.

Next, a mixture containing 7.8 g of the monomer solution and 0.2 g of compound C (color-developing compound or photoacid generator) was stirred in a 50 mL screw tube (the ratio of compound C was 2.5% by mass). A magnetic stirrer was used for stirring. During stirring, the temperature was set at 25° C., the rotational speed of the rotor was set at 500 rpm, and the stirring time was set at 5 minutes. After stirring, it was visually confirmed whether Compound C was dissolved in the monomer solution by such stirring without generating turbidity or precipitation. The chromogenic compound and the photoacid generator are respectively dissolved in the solutions of styrene, 4HBA, MMA, acrylic acid, NVP, 2MEA and methyl acrylate, and the mixed solution of 95% by mass of styrene and 5% by mass of 4HBA without producing turbidity or precipitation (compound C showed compatibility). On the other hand, the chromogenic compound and the photoacid generator were not dissolved in the respective solutions of 2EHA, lauryl acrylate, and stearyl acrylate, but turbidity or precipitation occurred (compound C did not show compatibility).

Furthermore, it was determined that the segment containing 80% by mass or more of the same monomer composition as that of the monomer solution in which Compound C exhibited the above-mentioned compatibility was within the microphase-separated structure by the polymer component having the segment. The phases formed are compatible. In addition, it was determined that the segment containing 80% by mass or more of the same monomer composition as that of the monomer solution in which Compound C did not exhibit the above-mentioned compatibility was separated into a microphase-separated structure by the polymer component having the segment. The phases formed within are not compatible. That is, the color-developing compounds and photoacid generators used in Examples 1, 2 and Comparative Example 1 respectively reacted to the hard segment (HS) formed in the microphase separation structure comprising 95% by mass of styrene and 5% by mass of 4HBA. The phase (the first phase in Example 1) has compatibility (in HS in Example 1, the proportion of the monomer (styrene, 4HBA) showing compatibility in Compound C is 80% by mass or more) . The chromogenic compound and the photoacid generator used in Examples 1, 2 and Comparative Example 1 have respectively to the phase (the first phase in the embodiment 2) formed in the microphase separation structure by HS comprising MMA as the main component. Compatibility (In HS in Example 2, the ratio of monomers (MMA, 4HBA) showing compatibility in Compound C was 80% by mass or more). In addition, the chromogenic compounds and photoacid generators used in Examples 1, 2 and Comparative Example 1 respectively reacted to the phases formed in the microphase separation structure of the soft segment (SS) containing 2EHA as the main component (Example 1 , the second phase in 2) did not have compatibility (in the SS in Examples 1 and 2, the proportion of the monomer (2EHA) in which the compound C did not show compatibility was 80% by mass or more).

<haze>

Regarding the PSA layer of each PSA sheet of Examples 1, 2 and Comparative Example 1, the haze was examined as follows. First, a sample for haze measurement is produced. Specifically, after peeling the release film (MRE#38) from the adhesive sheet, the adhesive layer side of the adhesive sheet (base film, adhesive layer) was attached to Eagle glass (thickness 0.55mm, loose wave Glass Co., Ltd.), and the substrate film (MRF#38) was peeled from the adhesive layer on the Eagle glass. Thereby, the sample for haze measurement (1st sample for measurement) was produced. Next, the haze of the pressure-sensitive adhesive layer in the sample was measured using a haze measurement device (trade name "HZ-1", manufactured by Suga Testing Instruments Co., Ltd.) (first haze measurement). In this measurement, the sample for measurement is set in the apparatus so that light is irradiated to the sample for measurement from the side of the Eagle glass. In addition, in this measurement, the measurement result obtained by measuring only Eagle glass under the same conditions was used as a reference line. The haze (before UV irradiation) of the adhesive layer obtained in this way is shown in Table 1.

On the other hand, for each of the PSA sheets of Examples 1 and 2 and Comparative Example 1, the haze after UV irradiation was examined as follows.

First, the same sample as the above-mentioned first measurement sample was produced. Next, the sample was irradiated with ultraviolet rays. Specifically, in an environment of 23° C. and a relative humidity of 50%, the adhesive sheet (adhesive layer) in the sample was irradiated with ultraviolet rays from the Eagle glass side through the glass (by this UV irradiation, the adhesive layer The colorless pigment reacts with the photoacid generator). In this UV irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device manufactured by Quark Technology Co., Ltd. (model "QEL-350-RU6W-CW-MY") was used as a light source, and the irradiation cumulative light amount was set to 8000 mJ /cm ² (accumulated light quantity of irradiation in the wavelength range of 320nm to 390nm). A measurement sample (second measurement sample) was produced in the above-mentioned manner.

Next, about the sample for 2nd measurement, the haze of the adhesive layer in a sample was measured using the haze measuring apparatus (trade name "HZ-1", manufactured by Suga Testing Instrument Co., Ltd.) (2nd haze measurement). Regarding the specific measurement method and conditions, the second haze measurement is the same as the above-mentioned first haze measurement. The haze (after UV irradiation) of the adhesive layer obtained in this way is shown in Table 1.

<Durability Test>

Regarding the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet of Examples 1, 2 and Comparative Example 1, the degree of bleeding suppression of the formed discolored portion was examined as follows.

First, for each PSA sheet of Examples 1, 2 and Comparative Example 1, a plurality of PSA sheets were prepared.

Next, by irradiating ultraviolet rays to the adhesive layer of the adhesive sheet through a photomask having linear openings, linear discolored portions are formed in the adhesive layer. The photomask is formed by a dry film photoresist disposed on the side surface of the substrate film in the adhesive sheet, and the line width of the opening of the photomask is about 200 μm (the opening of each photomask different line widths). In the ultraviolet irradiation, a UV-LED lamp with a wavelength of 365nm in the UV-LED irradiation device (model "QEL-350-RU6W-CW-MY") manufactured by Quark Technology Co. The pressure-sensitive adhesive layer was irradiated with ultraviolet rays, and the cumulative light quantity of irradiation was set to 2000 mJ/cm ² (cumulative light quantity of irradiation in a wavelength range of 320 nm to 390 nm).

Next, the line width of the linearly discolored portion formed on the pressure-sensitive adhesive layer was measured (measurement of the initial line width). Specifically, first, the linear discoloration part formed on the adhesive layer was observed with a digital microscope (trade name "VHX-900", manufactured by Keyence Corporation), and a part including the discoloration part and its nearby area. Then, binarize the captured image by image analysis software. Next, in the binarized image, the line width ( W1 ) of the linearly discolored portion is measured.

Next, the pressure-sensitive adhesive sheet in which the linearly discolored portion was formed in the pressure-sensitive adhesive layer was heat-treated at 85° C. for 120 hours (first durability test).

Next, the line width of the linearly discolored portion in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was measured. The measurement of the initial line width in the specific measurement method is the same as the above-mentioned measurement method. The line width W1 of the linear discoloration portion before the first durability test, the line width W2 of the linear discoloration portion after the first durability test, and the amount of change from the line width W1 to the line width W2 (|W2-W1|) Table 1 shows the rate of change (W2/W1) of the line width W2 with respect to the line width W1.

On the other hand, for the PSA layer of each PSA sheet of Examples 1, 2 and Comparative Example 1, except that the second durability test was carried out instead of the first durability test, the formed PSA layer was investigated in the same manner as above. Exudation inhibition degree of linear discoloration part. In the second durability test, the adhesive sheet having the linearly discolored portion formed in the adhesive layer was heat-treated at 65° C. and a relative humidity of 90% for 120 hours. The line width W1 of the linear discolored portion before the second durability test, the line width W3 of the linear discolored portion after the second durability test, and the amount of change from the line width W1 to the line width W3 (|W3-W1|) Table 1 shows the rate of change (W3/W1) of the line width W3 with respect to the line width W1.

The amount of change (|W2-W1|) and the rate of change (W2/W1) of the line width of the linearly discolored portion after the first durability test were smaller than those of Comparative Example 1 for each of the PSA sheets of Examples 1 and 2. Adhesive sheet. The amount of change (|W3-W1|) and the rate of change (W3/W1) of the line width of the linearly discolored portion after the second durability test were smaller than those of Comparative Example 1 for each of the PSA sheets of Examples 1 and 2. Adhesive sheet. That is, compared with the PSA sheet of Comparative Example 1, the change (deterioration) of the discolored part of the PSA layer in each PSA sheet of Examples 1 and 2 was suppressed.

The above-mentioned embodiments are examples of the present invention, and the present invention should not be construed as being limited to the embodiments. Modifications of the present invention that are obvious to those skilled in the art are included in the above claims.

Industrial applicability

The color-variable pressure-sensitive adhesive sheet of the present invention is used, for example, in bonding elements contained in a laminated structure of a display panel in a display panel manufacturing process.

Label description

S Adhesive Sheet (Color Changeable Adhesive Sheet)

10 adhesive layers

11 color changing part

20 base material

31 first member

32 second member.

Claims (9)

1. A color-changeable adhesive sheet having a color-changeable adhesive layer, wherein,

The adhesive layer comprises: a polymer component having a microphase-separated structure comprising a first phase and a second phase, a colorant capable of developing color by an external stimulus,

the colorant is compatible with the first phase and incompatible with the second phase.

2. The variable color adhesive sheet according to claim 1, wherein the polymer component comprises a polymer having a first segment and a second segment in a molecule, the first segment forming the first phase, the second segment forming the second phase.

3. The variable color adhesive sheet according to claim 2, wherein the polymer is a block polymer having a first polymer block as the first segment and a second polymer block as the second segment.

4. The variable color adhesive sheet according to claim 2, wherein the polymer is a graft polymer having a polymer main chain as the second segment and a polymer side chain as the first segment.

5. The variable color adhesive sheet according to claim 1, wherein a mass ratio of the second phase in the polymer component is larger than a mass ratio of the first phase.

6. The variable color adhesive sheet according to claim 1, wherein the colorant is a compound that develops color by reaction with an acid, and the adhesive layer further contains a photoacid generator.

7. The variable color adhesive sheet according to claim 6, wherein the photoacid generator is compatible with the first phase and not compatible with the second phase.

8. The variable color adhesive sheet according to claim 1, wherein a first color change width W1 of a color change region formed in the adhesive layer by applying the external stimulus thereto in a line shape, and a second color change width W2 of the color change region after further heat-treating the adhesive layer at 85 ℃ for 120 hours satisfy 0.5.ltoreq.w2/w1.ltoreq.2.

9. The variable color adhesive sheet according to claim 1, wherein a first color change width W1 of a color change region formed in the adhesive layer by applying the external stimulus thereto in a line shape, and a third color change width W3 of the color change region after further heat-treating the adhesive layer at 65 ℃ and a relative humidity of 90% for 120 hours satisfy 0.5.ltoreq.w3/w1.ltoreq.2.3.